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An extensive experimental study has been conducted to investigate the performance and stability of a supersonic axisymmetric mixed compression air intake. The intake has been designed for a free stream Mach number of 2.0. However, tests were conducted for free stream Mach numbers of 1.8, 2.0, and 2.2. This investigation is aimed to study effects of Mach number and back pressure on the intake flow stability during the buzz phenomenon. Further, the effect of acoustic resonance on the Buzz frequency has been investigated. Buzz phenomenon is defined as the shock oscillation ahead of the intake that may occur when the intake mass flow ratio reduces. Results show that the stability margin reduces when the free stream Mach number increases. In addition, reducing the free stream Mach number and increasing the back pressure cause the oscillation frequency to increase. The main cause of instability start is flow separation on the compression ramp and two ranges of frequency of buzz oscillations are obtained, range of 100 Hz for flow instability for Mach numbers of 1.8, 2.0 and 2.2, and range off 475 Hz for flow instability in Mach number of 1.8. For both cases, the spatial domain of buzz oscillations covers the entire intake length. Further, this low and high frequency ranges have significant conformity with the zeroth-order and first-order of the acoustic resonance frequency, respectively, that increase the probability of existence of acoustic resonance driving the buzz oscillation.

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Vehicle vibration and noise characteristics play a major role in ride comfort. Noise of tire in contact with the road is one of the main sources of noise in passenger cars, caused by the rolling of tire on uneven surfaces. Excitation imports through tread structure to fluid cavity and noise and vibrations transmission to the rims is of particular importance. In this paper, vibration analysis of coupled acoustic model of tire, rim and fluid acoustic cavity is performed. For this purpose, a coupled numerical finite element model is used. First, tire modeling has been addressed, taking into account the tread and two side walls and steel wheel rim. Then modal analysis has been performed to identify the structural and acoustic resonance frequencies and mode shapes. Then, using the harmonic environment coupled with static and modal analyses, acoustically coupled models of tire, rim and cavity are used to calculate the acoustic pressure of the fluid cavity, and sound pressure level, and the harmonic frequency response of the wheel hub system including the forces of wheel hub is discussed. According to the presented model, the parameters affecting tire noise levels are discussed.